Portable crimping tools for attachment of side panels to automobile doors are known. One tool of this type is disclosed, for example, in Canadian Pat. No. 889,616, issued Jan. 4, 1972. However, the crimping head of these tools generally include a pivoted hammer which requires a certain amount of working space in order to be inserted between the door and the body of a car on the edge side of the doors. With the general reduction in the size of the cars in the recent years, these tools are becoming too big and cannot be used any more on the hinge side of the doors for an increasing number of cars, so that it is necessary to remove the doors from the hinges and re-hang the doors after clamping of a new panel. This operation is time-consuming and adds up to the cost of labor which is now getting unreasonably high.